Electronic circuits for detecting measured quantities are fundamentally known from the prior art. Circuits of this kind usually have at least one sensor unit for generating an analog measurement signal, which represents a measured quantity detected by the sensor. Electronic circuits of this kind also have a signal detecting unit, which is, as a rule, integrated into a control unit, particularly in the automotive field. The signal detecting unit usually has a first analog/digital converter for digitizing the analog measurement signal. These electronic circuits are also associated with a voltage supply unit to provide a supply voltage for both the sensor unit and the signal detecting unit.
Traditionally, both the sensor unit and the signal detecting unit are operated from the same voltage source, with quantitatively equal supply voltages, these supply voltages being subject to the same error tolerance or imprecision. Because of this uniformity of the imprecisions in the voltage supply signals, this is also referred to as a simultaneous or ratiometric voltage supply.
Basically, it is assumed that the imprecisions or fluctuations in the supply voltage in the sensor unit also affect the analog measurement signal that it generates. Because of the subsequent digitizing of the analog measurement signal by an analog/digital converter, which is operated with a synchronous supply voltage, i.e. one that has the same imprecisions as that of the sensor unit, these imprecisions are compensated for in the digitized measurement signal emitted at the output of the analog/digital converter. Therefore with a traditional ratiometric supply of voltage to both the sensor unit and the signal detecting unit, fluctuations in the supply voltage have no effect on the measurement signal. The reason for this is that if these fluctuations occur, they do so to the same degree in both the sensor unit and the signal detecting unit and are therefore imperceptible and/or cancel each other out.
Future control units and/or signal detecting units will probably be operated with a quantitatively lower supply voltage than the present standard of 5 V. The components contained in the signal detecting units such as microcontrollers or analog/digital converters, particularly embedded analog/digital converters, will therefore also be operated with the lower supply voltage, for example 3.3 V. But at least for a transition period, the existing sensor units will continue to be used, which will still be operated preferably with 5 V. As a result, different voltage sources must be provided for the different supply voltages for the sensor unit and the signal detecting unit. There is therefore a significant risk of losing the ratiometry in the voltage supply, i.e. the homogeneity of the imprecisions of the two supply voltages, and therefore also the above-described advantage of the compensation for the imprecisions in the measurement signal. The reason for this is essentially that the different voltage sources for the separate supply voltages can have different individual imprecisions with regard to their voltage supply.
Based on this prior art, the object of the invention is to modify the known electronic circuit for detecting measured quantities, a method for operating such a circuit, and a computer program for executing this method in such a way that even when the sensor unit and the signal detecting unit are each supplied with respective supply voltages of differing precision, these different precisions are prevented from affecting the measurement signal emitted by the signal detecting unit.
This object is attained by the subject of claim 1, which proposes that the signal detecting unit have a correction unit that compensates for the effects of the imprecisions x1 and/or x2 on the digitized measurement signal in response to a digitized voltage signal representing the imprecision of the first supply voltage and emits a compensated digital measurement signal resulting from this compensation.
It should in particular be noted at this point that the analog measurement signal is generated by the sensor unit, which is operated with the first supply voltage that has an imprecision of x1. The analog measurement signal is then digitized by the first analog/digital converter, which is operated with a second supply voltage that has an imprecision of x2.